Method of producing oils of low pour point



Patented June 30, 1936 UNITED STATES PATENT OFFICE Carl Winning and Philip L. Young, Elizabeth, N. J., asslgnora to Standard Oil Development Company No mm. Application July 29, 1922, Serial No. 626,212

8 Claims. (Cl. 196-1) The present invention relates to the 'production of oils of low pour point and more speciflcally to the reduction of pour points of heavy oils of high viscosities and especially of the residual oils by means of substances of the class of pour inhibitors. Our invention will be fully understood from the following description.

Heavy viscous petroleum cuts of the type used for lubricants such as the heavier distillates and 10 residuals such as bright stocks, cylinder 'oilsand the like are generally characterized by high pour points, for example 40' or 50, or even 75 F.

These oils may be dewaxed by centrifugal or by cold settling but such operations are/expensive. The pour point of the lighter lubricating oils say of 'lfiseconds Saybolt viscosity at 210 F. or below, may be readily reduced to a substantial degree by the addition of substances of the class of pour inhibitors, but it has been observed that these materials are not especially sensitive when used in heavier distillates or the residues as mentioned before. 1

We have found that lack of sensitiveness of pour inhibitors in the heavier oils may be due to several factors but that among these the principal one is an interference caused by the presence of even minute amounts of the high molecular weight substances which are colloldally dispersed through the oil and which are generally of an asphaltic character. We do not wish to limit ourselves to any particular theories of operation of pour inhibitors in general,or the interference caused by colloidal dispersions, but we believe that the colloidal particles tend to adsorb on their surfaces the active ingredients of the pour inhibitor so as to remove it from the sphere of action when wax precipitation occurs and,

therefore, the pour inhibitor cannot exert its.

beneficial effects on the wax. Whatever the true explanation may be, we have observed that colloidal particles exert an undesirable influence on the pour inhibitors and that by their removal or reduction to extremely small proportions, the oils are greatly improved with respect totheir sensitivity toward pour inhibitors.

The colloidal materials which are generally present'in heavy crude oils are principally-of the asphaltlc or resinous type and due to their extremely high molecular weights are not perfectly soluble in the oil. It is possible but difficult to separate these materials by dialysis and similar methods because of the viscosity of the oil and it is believed that'the materials are of colloidal dimensions since they cannot be readily observed by optical means.

Our method consists in the removal of the colloidal substances naturally present in heavy residues and the heavier distillates to as complete a degree as possible before the addition of the pour inhibitor, and any desirable means suitable 5 for this purpose may be adopted. As indicated above, dialysis and similar methods are diflicult, slow and generally unsatisfactory as practical refining methods, although they may be used. Distillation of the oil under very high vacuum to 10 prevent decomposition is satisfactory, although great precaution should be taken to prevent entrainment of the tarry particles of unvaporized liquid, such as the use of vapor baflles, cyclone separators, mist extractors and the like which are 15 of well known design. It is desirable to take off a normal distillate out between. the bottoms and the oil to which the pour inhibitor is to be added.

It is also difficult to vaporize the heaviest oils, but various expedients may be adopted, for example, 20 diluting the oil'with a lighter stock and causing vaporization by heating the oil to a high temperature and suddenly releasing pressure, so that the lighter constituents assist in the vaporization of the heavier oil. It may be necessaryv to repeat 25 the distillation more than once, or to combine the vacuum distillation with other purification means so as to reduce the concentration of the colloidal bodies to below the critical proportion necessary for a substantial increase of sensitivity. 30 Other separation means such as the agglomeration of the colloid by means of acid of the type of sulphuric, or by the use of solvents which dissolve the oil but precipitate the colloids may be used. Of these solvents naphtha or preferably, the low- 5 er hydrocarbons such as propane, butane, pentane or their mixtures with each other or with small amounts of ethane or ethylene, or alcohols such as methyl, ethyl, propyl, butyl and the higher ones may be used, as well as the esters of the type 40 of methyl, ethyl, propyl formates, acetates and the like; and ketones, among which acetone, methyl-ethyl and (ii-ethyl may be mentioned. All of these solvents may be used in admixtures with each other or with naphtha for our pur- 45 poses. These solvents mix with the oil at ordinary or at slightly reduced temperatures, but

phenol, -fu'rfurol and liquid sulphur dioxide.

'i'hese'have the property of dissolving the colloidal asphalt and it may be thus separated from 55 the oil. It is often advantageous to use a solvent of these classes to dilute the oil and then to treat with sulphuric acid, the acid acting as an agglomerating agent for the materials which are precipitated. Other agglomerating agents or adto the action of pour inhibitors and below which they are sensitive roughly in proportion to the concentration of the inhibitor. It is extremely diflicult to state the exact concentration of these materials for the reason that the amounts are always very small and there is no means of being certain that all of the material is removed from the oil. Furthermore. the character of the colloidal particle also affects the sensitivity of the oil. In some instances relatively small amounts of the colloidal particles exert a high degree of interference, whereas in other cases evendarger amounts exert less pronounced effects and this is to be attributed, in our belief, to the specific character of the colloidal particle.

The best method to determine the degree of purity necessary for sensitivity is by empirically treating the oil andfrom time to time testing its sensitivity with al standard pour inhibitor. Naturally, it is undesirable to treat the 011 more vigorously than is required for the purpose in hand. The critical amount is quite minute and is generally well above the quantity naturally found in residual oils even of the purest parailin base type represented by the Pennsylvania oils when reduced to viscosities above 75 or 85 seconds Saybolt.

The pour inhibitors which we intend to use make up a rather large class of materials which have the power to influence either the crystal densation may be carried out in any desired manner, for example by chlorinating the wax and causing the condensation through the agency of catalysts oi the type of aluminum chloride. Poly-' mers produced by the condensation of chloroparaflin alone are also satisfactory, as well as polymers produced during the condensation of oxygen-containing aliphatic materials with long paraflin chains such as acids, esters, alcohols, ke-

tones and the like or the condensation of such materials in the presence of aromatics. The con-' densation of these materials may be carried out,"

as indicated before, by chlorination of the aliphatic material and condensation with aluminum chloride or, if the paraflln hydrocarbon be unsaturated, the condensation may be obtained directly. Or, another class of pour inhibitors, me-' tallic salts, may be used, such as the zinc and magnesium salts of acids produced by the oxidation of paraffin wax, or the zinc and magnesium salts of hydroxy stearic acid and its hmnologues, or of aluminum stearate, oresters'such as of the higher fatty acids, esters of the alkylol-' amines, for example, triethanolamine, stearate, or

diethanolamine ester of acids produced by the oxidation of paramn wax. There are other types of pour inhibitors, as well, such as oil soluble cellulose compounds, ethers or esters which have hydrocarbon groups containing a total of at least 20 carbon atoms, for example cellulose stearate, or the trilaurate or the stearyl ethers and the like.

All of these become considerably more sensitive in heavier oils which are treated according to the present methods.

As an example of the present method the following experiments may be considered as illustrative:

The original oil with a pour point of 40 F. showed little or no sensitivity to pour inhibitors, for example, the pour was reduced by some 5 or 10 F. by the same pour inhibitor which will be used in the experiment below.

The oil is diluted with about 10 volumes of propane containing 10% of ethane maintained under pressure suflicient to hold it in a liquid state and at room temperature. On complete mixing and settling two layers were observed, the majority of the original oil being present in the upper layer. This layer is carefully decanted and after reducing pressure and gradual heating, the solvent is completely evaporated leaving an oil which is improved in color and whichhas a pour point of 60F. On addition of 2% of'the polymer produced by the reaction of chlorparaffln and naphthalene with aluminum chloride and which showed little sensitivity in the original oil, the pour point of the treated oil is reduced to +20 F. In other words, the treated oil containing the polymer remains fluid 20 degrees lower thanthe original oil.

If the oil with the 60 F. pour point is partially above reduced the pour point to zero, and ii further treatment with the solvent is repeated according to the method outlined above, the effectiveness of the pour inhibitor may be sufiicient to reduce the pour point to below zero. I

As a further example of the operation of our process a heavy residual oil having a viscosity of 130 seconds Saybolt at 210 F. is filtered through clay after dilution with naphtha in the usual method. The pour point of the oil is 60 F. It is found to be relatively insensitive to 1% of the pour inhibitor used in the prior example which reduced the pour point to only 50 F. If the clay filtration, however, is repeated, an oil of 60 F. pour is. again produced which, however, is reduced to 35 F. by addition of 1% of the inhibitor used above. This oil can also be partially dewaxed before the addition of the pour inhibitor to reduce its pour point to 30 or 35 F. and then ducedtozero or below.

Our method is or particular value-in treatment of. residual oilswhich are generally richest in colloidal asphalt, but it is at the same time apto their mode of production orfor other reasons are contaminated with asphaltic or other colloidal materials. e

- The present invention is not to be limited to on addition of the pour inhibitor it may be replicable to treatment of distillate oil which due anyparticular method of removing colloidalmathe following claims in which we wish to claim all novelty inherent in the invention.

We claim:

1. An improved process for reducing the pour point of waxy residual oils containing asphaltic or resinous impurities comprising separating such impurities by solvent precipitation and adding to the purified oil a synthetic pour inhibitor.

2. Process according to claim 1 in which the solvent precipitation is accomplished by means of a light hydrocarbon solvent.

3. Process according to claim 1 in which the precipitating solvent is used in conjunction with an agent for agglomerating the precipitated impurities.

4. Process according to claim 1 in which the synthetic pour inhibitor is a condensation product of a waxy hydrocarbon.

5. Process according to claim 1 in which the pour inhibitor is a condensation product of a waxy hydrocarbon and an aromatic hydrocarbon.

6. Process according to claim 1 in which the inhibitor is a low temperature, aluminum chloride condensation product of chlorinated paraflin 10 wax and naphthalene.

CARL WINNING. PHILIP L. YOUNG. 

